List of anatomical variations

This article provides a comprehensive list of anatomical variations, which are naturally occurring differences in human morphology. These variations are not considered defects or abnormalities but rather normal deviations that do not inherently indicate pathology.

Head and neck

Skeletal variations

Occipitalization of the atlas
Basilar tubercle of clivus
Clivus bony canal
Condylus tertius
Epipteric bone
Foramen tympanicum
Ossified petrosphenoid ligament
Ossification anomalies of the atlas (C1)
Craniopharyngeal canal
Canalis basilaris medianus
Fossa navicularis magna
Transverse basilar fissure (Saucer's fissure) (see Clivus)
Arcus praebasiocipitalis
Stafne bone cavity
Arcuate foramen
Ossiculum terminale (of dens)
Os odontoideum
Intermediate condylar canal
Innominate canal of Arnold
Arcus praebasiocipitalis
Inca bone
Haller cell
Sphenoethmoidal air cell (Onodi cell) (see Sphenoid sinus)
Accessory maxillary ostium (see Maxillary sinus)
Thyroid foramen (see Thyroid cartilage)
Collateral eminence
Wormian bones

Muscular variations

Levator glandulae thyroidea (levator muscle of thyroid gland)
Accessory belly of digastric muscle (see Digastric muscle)
Atlantomastoid muscle^[1]
Styloauricularis muscle^[2]
Transversus nuchae muscle
Pterygoideus proprius muscle
Levator claviculae muscle
Levator glandulae thyroidea muscle
Cleidoatlanticus muscle
Cleidocervical muscle
Cleidofascialis muscle
Cleidohyoideus muscle
Cleidomastoideus muscle
Cleido-occipitalis cervicalis muscle
Cricocorniculate muscle
Cricohyoid muscle (variation of thyrohyoid)
Sternoclavicularis anticus muscle
Styloauricularis muscle

Vascular variations

Persistent primitive olfactory artery
Artery of Percheron
Stapedial artery
Thyroid ima artery
Fourth thyroid vein (of Kocher) (see Inferior thyroid veins)
Falcine sinus
Hypoglossal artery
Persistent left superior vena cava
Trigeminal artery

Nervous variations

Trigeminal nerve duplication
Aberrant facial nerve course
Accessory hypoglossal nerve

Other variations

Preauricular sinus
Supernumerary nipple
Darwin's tubercle
Anisocoria
Diagonal ear lobe crease
Empty sella turcica
Epicanthic fold
Crease of the upper eyelid (Single or Double eyelid)
Zuckerkandl's tubercle
Pyramidal lobe of thyroid gland

Vertebral column and ribs

Skeletal variations

Atlanto-occipital fusion (see Atlanto-occipital joint)
Butterfly vertebrae
Cervical ribs
Coccygeal ribs
Block vertebrae
Sagittal cleft vertebrae
Lumbosacral transitional vertebrae
Split cord malformation
Sternal cleft
Spondylolisthesis
Oppenheimer's ossicle
Spondylolysis
Sprengel's deformity

Thorax

Skeletal variations

Sternal foramen and xiphoid foramen
Episternal ossicles
Manubriosternal fusion (see Sternum)
Sternoxiphoidal fusion
Bifid xiphoid process (see Xiphoid process)
Bifid rib

Muscular variations

Sternalis muscle (rectus thoracis)
Costocoracoideus muscle

Other variations

Azygos lobe of the lung
Tracheal bronchus (see Bronchus)
Cardiac bronchus (see Bronchus)
Supernumerary lung fissures
Horseshoe lung

Upper limb

Skeletal variations

Bifurcated clavicle
Coracoclavicular joint
Os acromiale (see Acromion)
Carpal coalition
Carpal boss
Bipartite capitate
Supracondylar process of the humerus
Scapular foramina and tunnels

Muscular variations

Accessory subscapularis muscle
Gantzer's muscle (see Flexor pollicis longus muscle)
Chondroepitrochlearis muscle (see Pectoralis major)
Coracocapsularis muscle
Costodeltoideus muscle
Axillary arch muscle
Epitrochleoanconeus (anconeous epitrochlearis) muscle
Extensor medii proprius muscle
Extensor digitorum brevis manus muscle
Extensor indicis et medii communis muscle
Extensor pollicis et indicis communis muscle
Extensor carpi radialis tertius (extensor carpi radialis accessorius) muscle
Linburg-Comstock variation (conjoint flexor pollicis longus and flexor digitorum profundus of the index)
Palmaris profundus muscle
Flexor carpi radialis profundus muscle
Ulnaris quinti muscle
Pisiuncinatus muscle (pisohamatus)
Sternohumeralis muscle
Sternochondrocoracoideus muscle
Subscapularis minor muscle
Tensor semivaginae articulations humeroscapularis muscle
Thoracobrachialis muscle^[3]

Vascular variations

Alar thoracic artery
Median artery
Superficial ulnar artery
Variation of the basilic vein

Nervous variations

Bifid median nerve (see Median nerve)
Nerve of McKenzie
Martin-Gruber anastomosis
Riché-Cannieu anastomosis
Berrettini anastomosis
Froment-Rauber nerve

Other variations

Accessory nail of the fifth toe
Osborne's ligament
Struthers' ligament

Lower limb

Skeletal variations

Femoral anteversion/retroversion
Os tibiale externum
Fabella (popliteal sesamoid)
Calcaneonavicular coalition
Accessory navicula
Talocalcaneal coalition
Cyamella (popliteal fabella)
Sesamoid bone of the second, third, fourth, and fifth finger
Talus accessorius

Muscular variations

Accessory soleus muscle
Accessory popliteus muscle
Adductor minimus muscle
Tensor fasciae suralis muscle
Gastrocnemius tertius muscle (see Gastrocnemius muscle)
Gluteoperinealis muscle
Gluteus quartus muscle
Popliteus biceps muscle
Fibularis (peroneus) quartus muscle
Peroneocalcaneus internus muscle

Vascular variations

Marginal artery of the colon
Corona mortis (see Obturator artery)

Nervous variations

Sciatic nerve variations in relation to the piriformis muscle

Abdomen

Muscular variations

Interfoveolar muscle
Saphenous muscle
Pubotransversalis muscle

Vascular variations

Arc of Bühler
Third mesenteric artery
Marginal artery of the colon (of of Drummond)

Other variations

Accessory spleen
Annular pancreas
Bifid pancreas tail
Double common bile duct
Agenesis of vermiform appendix (see Appendix (anatomy))
Colon duplication
Accessory pancreatic duct
Pancreas divisum
Gastropancreatic ligament

Pelvis

Vascular variations

Uterine artery anastomoses variations

Other variations

Bladder exstrophy
Renal artery anomalies
Splenogonadal fusion
Supernumerary ovaries
Horseshoe kidney (Ren arcuatus)
Hirsuties coronae glandis

References

^ Lee, Rebecca; Pang, Stephen C.; Borman, William H.; Herrin, Sean O.; Bale, Logan S. W. (2022-10-01). "A prevalence study of the atlantomastoid muscle". Surgical and Radiologic Anatomy. 44 (10): 1349–1353. doi:10.1007/s00276-022-03022-6. ISSN 1279-8517. PMID 36155834.
^ Touré, Gaoussou; Anzouan-Kacou, Evelyne (2016-10-01). "The styloauricular muscle: clinical relevance and literature review of this rare muscle". Surgical and Radiologic Anatomy. 38 (8): 983–986. doi:10.1007/s00276-016-1633-x. ISSN 1279-8517. PMID 26846137.
^ Zielinska, Nicol; Karauda, Piotr; Węgiel, Andrzej; Szewczyk, Bartłomiej; Olewnik, Łukasz (2023-11-01). "A very rare case of a thoracobrachialis muscle". Surgical and Radiologic Anatomy. 45 (11): 1493–1496. doi:10.1007/s00276-023-03240-6. ISSN 1279-8517. PMC 10587252. PMID 37733018.

[1] Lee, Rebecca; Pang, Stephen C.; Borman, William H.; Herrin, Sean O.; Bale, Logan S. W. (2022-10-01). "A prevalence study of the atlantomastoid muscle". Surgical and Radiologic Anatomy. 44 (10): 1349–1353. doi:10.1007/s00276-022-03022-6. ISSN 1279-8517. PMID 36155834.

[2] Touré, Gaoussou; Anzouan-Kacou, Evelyne (2016-10-01). "The styloauricular muscle: clinical relevance and literature review of this rare muscle". Surgical and Radiologic Anatomy. 38 (8): 983–986. doi:10.1007/s00276-016-1633-x. ISSN 1279-8517. PMID 26846137.

[3] Zielinska, Nicol; Karauda, Piotr; Węgiel, Andrzej; Szewczyk, Bartłomiej; Olewnik, Łukasz (2023-11-01). "A very rare case of a thoracobrachialis muscle". Surgical and Radiologic Anatomy. 45 (11): 1493–1496. doi:10.1007/s00276-023-03240-6. ISSN 1279-8517. PMC 10587252. PMID 37733018.

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